Present computer systems typically use hard-disk drive systems for mass storage. An exemplary hard disk drive read channel of the prior art is shown at FIG. 1. A magnetic surface of the hard disk 101 induces electrical signals in the read head 103. The data rate of these signals varies with each zone of the hard disk drive. These read signals are amplified by preamplifier circuit 105 and applied to variable gain amplifier 109 and programmable analog filter 111 of the read channel analog front end 107. The programmable filter performs anti-aliasing and channel equalization for analog-to-digital (ADC) circuit 113. This ADC circuit subsequently produces digital signals suitable for digital processor 115.
Conventional design techniques may not be adequate for state-of-the-art read channel applications for several reasons. First, a native tolerance of resistor-capacitor (RC) products is typically .+-.40%. Such variation is incompatible with a required filter group delay accuracy of .+-.5% at a high corner frequency of 100 MHz. Second, variable gain amplifier (VGA) gain and bandwidth requirements for conventional techniques may require a relatively large unity-gain bandwidth of 5.85 GHz. Finally, conventional attempts to avoid gain-bandwidth limitations may result in an increase in power dissipation.